sp hybridization is the mixing of one s orbital and one p orbital on a central atom to form two equivalent hybrid orbitals (each 50% s, 50% p character), producing a linear geometry with 180° bond angles and leaving two unhybridized p orbitals available for pi bonding.
sp hybridization happens when an atom blends one s orbital with one p orbital to make two identical hybrid orbitals. Each hybrid is half s character and half p character. Those two hybrids point in exactly opposite directions, which is why sp-hybridized atoms sit in a linear arrangement with 180° bond angles.
Here's the part the AP exam loves. Hybridizing only one of the three p orbitals leaves two unhybridized p orbitals behind. Those leftover p orbitals overlap side-by-side to form pi bonds. That's why sp hybridization shows up wherever you see triple bonds (like the carbons in acetylene, HC≡CH) or an atom with two double bonds (like the central carbon in CO₂). A quick shortcut you can trust on the exam is to count regions of electron density around the atom. Two regions, whether they're bonds or lone pairs, means sp.
This term lives in Topic 2.7 (VSEPR and Bond Hybridization) in Unit 2: Compound Structure and Properties, supporting learning objective 2.7.A. That objective asks you to connect Lewis diagrams, VSEPR theory, bond orders, and hybridization to explain a molecule's structural and electronic properties. sp hybridization is the bridge between two skills you've already built. VSEPR tells you that two electron domains repel each other into a linear shape, and hybridization explains which orbitals the atom actually uses to make that happen. It also explains where pi bonds come from, which connects directly to bond order, bond energy, and bond length comparisons. If you can identify sp hybridization, you can justify why a triple bond is shorter and stronger than a double or single bond.
Keep studying AP Chemistry Unit 2
Linear Molecular Geometry (Unit 2)
sp hybridization and linear geometry are two descriptions of the same situation. Two electron domains push apart to 180°, and the two sp hybrids are the orbitals that point in those opposite directions. If the question says linear with no lone pairs distorting things, think sp.
Triple Bond & Acetylene (Unit 2)
A triple bond is one sigma bond plus two pi bonds, and those two pi bonds come from the two unhybridized p orbitals left over after sp hybridization. Acetylene (HC≡CH) is the classic example, with both carbons sp-hybridized and the whole molecule perfectly linear.
sp2 and sp3 Hybridization (Unit 2)
The pattern is just counting. Mixing in more p orbitals gives more hybrids and a wider spread of angles. sp gives 2 hybrids at 180°, sp² gives 3 at 120°, sp³ gives 4 at 109.5°. Each step up in hybridization means one fewer leftover p orbital for pi bonding.
Bond Order and Bond Energy (Unit 2)
Under LO 2.7.A you compare relative bond energies using bond order. sp-hybridized atoms host the highest bond orders (triple bonds), so spotting sp hybridization lets you argue that a C≡C bond is shorter and stronger than C=C or C–C.
sp hybridization is a multiple-choice staple. Common stems ask you to identify which species has an sp-hybridized central atom (CO₂ and HC≡CH are the go-to answers), to count sigma and pi bonds in acetylene (3 sigma, 2 pi), or to state the ideal bond angle for sp hybridization (180°). The trap answers usually mix up hybridization with bond count, so remember to count electron domains, not individual bonds. No released FRQ has asked for the term verbatim, but FRQs regularly hand you a Lewis structure and ask you to justify geometry, bond angles, or relative bond lengths. Naming the hybridization and the leftover p orbitals is exactly the kind of particulate-level reasoning that earns those points.
Students mix these up because both involve double or multiple bonds. The difference is the number of electron domains. sp means two domains (linear, 180°, two unhybridized p orbitals, so it can support a triple bond or two double bonds). sp² means three domains (trigonal planar, 120°, only one unhybridized p orbital, so at most one pi bond). A carbon with one double bond and two single bonds is sp², not sp.
sp hybridization mixes one s orbital with one p orbital to form two equivalent hybrid orbitals, each with 50% s and 50% p character.
An sp-hybridized atom has exactly two regions of electron density, giving a linear arrangement with 180° bond angles.
Hybridizing only one p orbital leaves two unhybridized p orbitals, which form the two pi bonds in a triple bond or in two double bonds.
Acetylene (HC≡CH) is the classic sp example, with two sp-hybridized carbons, 3 sigma bonds, and 2 pi bonds total.
CO₂ is also sp-hybridized at carbon because two double bonds still count as just two electron domains.
The shortcut for any hybridization question is to count electron domains on the atom: 2 means sp, 3 means sp², 4 means sp³.
sp hybridization is the mixing of one s orbital and one p orbital to create two equivalent hybrid orbitals pointing 180° apart. It's tested in Topic 2.7 (Unit 2) and explains linear molecules like CO₂ and acetylene.
No. A triple bond guarantees sp hybridization, but sp doesn't guarantee a triple bond. The carbon in CO₂ is sp-hybridized with two double bonds, and BeCl₂'s central atom is sp with only single bonds. What sp really means is two electron domains.
sp has two electron domains (linear, 180°) and two leftover p orbitals for pi bonding, while sp² has three domains (trigonal planar, 120°) and only one leftover p orbital. Count the domains around the atom and the answer falls out.
180°. The two sp hybrid orbitals point in exactly opposite directions, which is why sp-hybridized atoms produce linear geometry. This shows up as a direct multiple-choice question on the AP exam.
Acetylene has 3 sigma bonds (two C–H and one C–C) and 2 pi bonds (both inside the C≡C triple bond). Both carbons are sp-hybridized, and the two pi bonds come from their unhybridized p orbitals.